Improved Holography For Chirped Waveguide Diffraction Gratings

Diffraction gratings on planar waveguides have been improved by removing holographic causes of unwanted scattering of guided waves and by increasing the grating depth to obtain greater diffraction efficiency. Viewing the gratings as holograms of the exposure system permitted identifying and removing offending components such as collimating lenses. Reducing the standing wave pattern in the film during exposure permitted greater groove depth in the resulting grating.